<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        //递归
        function one(n) {
            if (n == 1 || n == 2) {
                return 1;
            }
            return one(n - 1) + one(n - 2)
        }
        console.log(one(20))

       
    </script>
</body>

</html>